Dewatering device for wet magnetic drum separator



Aug- 4, 1970 R. A. STECKHAN 3,522,883

DEWATERING DEVICE FOR WET MAGNETIC DRUM SEPARATOR Filed April 2G, 1968 /A/l/fA/Toe United States Patent O U.S. Cl. 210-222 9 Claims ABSTRACT OF THE DISCLOSURE A wet magnetic drum separator of the type which rotates while partially immersed in a slurry containing magnetic material while backed by a magnet is provided with a dewatering device beyond its exit position from the slurry. In a preferred form, the dewatering device is a pivotally or hingedly mounted bar having a magnetic pontion which is attracted by the magnet of the separating drum against the drum surface to break the miniscus of water on magnetic particles carried by the drum surface to remove water from the particles before they are released from the drum surface. The water can be returned to the slurry.

BACKGROUND OF TI-IIEl INVENTION Field of the invention This invention relates to magnetic separators of the type using a conveyor backed by a stationary magnet for removing magnetic materials from a slurry or the like and more particularly relates to the recovery of magnetic particles in a more concentrated form.

Description of the prior art Magnetic drum separators are conventionally used for separating magnetic particles from slurries and the like. Suitable separators are disclosed by Buus et al. in U.S. Pat. No. 2,992,736, by Buus in U.S. Pat No. 2,992,737 and by Greenwald in U.S. Pat. fNo. 3,146,191. However, in some separations it is desired to obtain a concentrated or even dried magnetic material product from a liquid slurry.

'For example, in heavy media separation processes for the separation of coal, gravel, ores and minerals from waste products, it has been proposed to form a slurry or mixture of finely divided magnetite and/or ferrosilicon particulate material with water to provide a separation bath of a predetermined specific gravity. The coal, ore, or other material to be separated is introduced into the bath and the materials having a higher specific gravity than the bath sink Ito the bottom while the materials having a lower specific gravity than the bath oat oi the top. The separated materials are drained of excess liquid and passed over vibrating screens where the particulate bath materials, i.e., magnetite or ferro-silicon, and fines are washed from the recovered products. Because of the ferro-silicon and magnetite are of value, these must be recovered and recirculated to the bath if the operation is to be economical. Therefore, washings from lthe vibrating screens containing these materials are fed to wet magnetic drum separators where the magnetic materials are recovered. Because of the criticality of the specific gravity of the initial separation bath to which the magnetic materials are to be returned, the magnetic materials discharged from the drum separators are conventionally subjected to subsequent dewatering treatment to remove excess water and raise the specific gravity of the magnetic material prior to its reintroduction into the bath so as not to adversely influence the specitic gravity of the bath.

3,522,883 Patented Aug.. 4, 1970 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view through a wet magnetic drum separator embodying features of this invention; and

FIG. 2 is an enlarged portion of the separator of FIG. 1 better showing an embodiment of the dewatering device of this invention in association with the drum separator.

SUMMARY OF THE INVENTION The present invention provides a magnetic separator of the type useful in separating magnetic materials from liquids and slurries. The separat-or includes a conveyor which is partially submerged in and moves through a body of the liquid while backed by a stationary magnet. The magnetic material is attracted by the magnet to a material-receiving surface of the conveyor and is conveyed out of the liquid and away from the field of influence of the magnet whereupon the magnetic material is released from the material-receiving surface at a release station. Between the position of exit from the liquid and the release station there is mounted a dewatering device which breaks the miniscus of water on the magnetic material and separates water from the magnetic material as it is carried on the conveyor surface.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the preferred form, the magnetic separator is a drum separator and the dewatering device is an elongate member having an extent the width of the drum and mounted to ride on the drum surface below the magnetic material-release station to press against magnetic material carried by the drum surface and thereby break the water miniscus and remove water from 'the material. The elongate member can be in the form of a bar, a roller or other shape and is preferably mounted for pivotal movement between positions engaging the drum and removed from the drum. In a specifically preferred form, the elongate member includes a magnetic portion which is attracted by the magnet backing the drum to urge the member toward the drum and against the magnetic material on the surface.

Referring now to the drawings, the elongate drum separator includes a framework 10 and a drum 11 mounted for rotation on a longitudinal shaft 12 which is secured at its ends to framework 10. The drum 11 has a cylindrical non-magnetic material receiving surface 11a preferably of material such as stainless steel. Drum 11 is driven in the direction of arrow `13 by suitable means such as a motor reducer drive, sprocket chain and sprocket wheel (not shown) fixed to the drum.

The slurry to be processed is introduced into the separator through inlet 14 into a chamber 1S which has an overiiow weir 16 over which the slurry is delivered to a container 17 for providing a body of slurry in which drum 11 is partially immersed. Container 17 has a distribution chamber portion configurated to deliver the incoming slurry close to the surface 11a of drum 11. The magnetic solids in the slurry are attracted to the rotating drum surface by a magnet means indicated at `18 which closely backs surface 11a of the drum. Magnet means 18 can comprise an arrangement of permanent magnets such as described by Buus, Buus et al. and Greenwald in the above identified patents and a description of those magnet arrangements is incorporated herein by reference. The magnetic material attracted to surface 11a is carried by surface 11a until it is out of the range of influence of the magnet 18 and is released from magnet 18. The nonmagnetic solids with the bulk of the water are carried to a tailing discharge at outlet 20. An operating water level is maintained in container 17 by outlet weir 21 over which excess water o'ws for discharge through outlet port 22.

Weir 21 maintains the approximate maximum water in container 17. For purposes of orientation, the drum surface I11a as it rotates enters the body of slurry at a drum surface entry station at 30 and the drum surface exits from the body of water at a drum surface exit station 31. The magnetic material release station is identified at reference numeral 32. A device for breaking the water miniscus and removing water from the magnetic material on surface 11a is mounted for operation between drum exit station 31 and magnetic material release station 32 and is shown generally at 40 in FIG. l. As best seen in FIG. 2, the device 40 includes a bar 41 of solid material, preferably nonmagnetic, e.g., metallic or plastic, which is sufficiently laterally elongate to track the entire width of surface 11a. Device 40 also preferably includes magnetic material such as steel plate 42 backing bar 41 so that bar 41 can be urged against the magnetic material on surface 11a by the inuence of magnet 18. Note that the assembly of bar 41 and plate 42 is pivotally mounted by hinge 43 for movement between a position with bar 41 urged against material on surface 11a as shown in full lines in FIG. 2 and a position where bar 41 is removed from surface 11a as shown in phantom in FIG. 2. This pivotal mounting also permits bar 41 to ride over the material on surface 11a and generally cornpensate for differences in material thickness while the drum is rotating. A plate or trough 45 is provided for directing magnetic material discharged at 19 from the separator and a second plate 46, which forms a portion of the wall structure of container 17, is provided for returning separated liquid to the body of slurry in tank y17. For convenience, hinge 43 is mounted to and supported by plate 45.

In operation of the device, bar 40 appears to function as a squeeze bar under magnetic attraction of magnet 18. As a result of the bar, the specific gravity of the discharged magnetic material product is raised considerably by removal of some of the excess water from the product. By thereby raising the specific gravity of the product at the discharge of the separator device, it is possible to return the discharged product directly to a heavy medium separation bath without subsequent dewatering since the product will not materially affect the specific gravity of the bar.

The percentage of solids in the slurry feed to the magnetic separator has a direct relationship to the percentage of solids in the concentrate from the magnetic separator. The higher the percentage of solids in the feed, the higher the percentage of solids in the concentrate. However, in all instances where the squeeze bar was uesd, the specific gravity of the concentrate was increased considerably. Table I is a table of direct test results utilizing all ferro silicon as the solids in the feed to the magnetic separator and at five different percentages of solids in the slurry feed to the magnetic separator, and the resultant specific gravity and percentage of solids of the discharge concentrate from the separator. Por comparison, with the same device but without the bar 40, the concentrate averages approximately 2.58 specific gravity.

Another series of six tests was conducted in which all of the solids in the feed to the magnetic separator consisted of magnetite, 'with results reported in Table II.

The separator without the squeeze bar 40 produces an average specific gravity of the concentrate of 2.18.

TABLE II Feed Concentrate Specific gravity Percent solids Specific gravity Percent solids l. 04 4. 9 2. 26 69. 8 1. O6 7. 0 2. 56 76. 1 1.17 18.2 26.0 76. 9 1. 19 20. 0 2. 64 77. 2 1.26 25. 8 2. 66 78. 0 l. 27 26. 4 2. 67 78. 3

Another series of six tests was conducted wml varying specific gravities in the feeds utilizing solids consisting of 50% magnetite and 50% ferro-silicon and which under normal separator conditions without the squeeze bar produced an average concentrate of 2.42 specific gravity. The results are reported in Table III.

During operation of the device in the above tests, the bar 40 was attracted by the magnetic field of magnet 18 so that as the magnetic materials are carried upward out of the inuence of the magnetic field by the rotating drum cylinder, a magnetic squeezing action was exerted by the bar against the cylinder, squeezing out excess moisture before the magnetic concentrate was discharged down the discharge chute 45.

A prime advantage of this preferred structure is that the dewatering pressure of bar 40 remains relatively constant for excellent water removal regardless of the quantity of magnetic material passing through the separator.

Although the present invention is susceptible of ernbodiment in many different forms, there has been shown in the drawings and has been described above in detail an embodiment of the invention with the understanding that the invention is not considered to be limited by the embodiment illustrated and described. Modifications for performing the water separation function will be apparent to those in the art and are to be considered within the spirit of the invention as defined in the following claims.

I claim:

1. A magnetic separator for wet magnetic separations comprising a container for containing a body of liquid into the container, a conveyor having a material receiving surface for receiving solid material to be separated from the liquid, a magnet assembly for tending to attract magnetic material against the material receiving surface for movement therewith, means mounting said conveyor for movement into and out of the body of liquid at entry and exit stations respectively, said magnet means backing said conveyor below the liquid level of said container and extending beyond said exit station, a release station beyond said exit station for releasing material attracted to said surface, and dewatering means between said exit station and release station miniscus and removing liquid from material on said conveyor, said last named means comprising a nonmagnetic member extending the width of the drum and a magnetic member supporting said nonmagnetic member, whereby said magnet means between said exit station and said release station attracts said magnetic member to urge said nonmagnetic member against said conveyor for breaking the liquid miniscus and for removing liquid from material on said conveyor surface.

2. The separator of claim 1 including means mounting said dewatering means for movement between a position against said conveyor surface and a position removed from said conveyor surface.

3. The separator of claim 2 wherein said mounting means comprises pivotally mounting said dewatering means for movement through an arc between said positions.

4. The separator of claim 3 wherein said conveyor means is a rotating hollow durm and said nonmagnetic member comprises a solid bar of nonmagnetic material extending the width of the drum for contacting the drum surface, and said magnetic member comprises a plate of magnetic steel backing said bar.

5. The separator of claim 1 including chute means deining a magnetic material outlet path from said release station.

6. The separator of claim 5 including hinge means Securing said dewatering means to said chute means for pivotal movement toward and away from the conveyor surface.

7. The separator of claim 5 including chute means defining a separate path for return of water from said dewatering means to said container.

8. The separator of claim 1 wherein said inlet means UNITED STATES PATENTS 2,410,601 11/1946 Crockett 209-232 X 2,564,515 8/1951 Vogel 209-229 X 3,295,678 1/1967 Genier 209-232 X 3,341,021 9/ 1967 Casson 209-229 X FOREIGN PATENTS 58,872 1/1938 Norway.

FRANK W. LUTTER, Primary Examiner 20 R. HALPER, Assistant Examiner U.S. Cl. X.R. 

